Wire and cable, whether used for the transmission of power or communications, are usually stored outside or in unheated areas before installation. If the insulation or jacketing becomes brittle at low temperatures and cracks, the integrity of the wire or cable is defeated and a short circuit with its attendant problems becomes a real possibility. Consequently, the specifications for the insulating or jacketing layers generally require that these materials pass a low temperature brittleness test. Low temperature performance of minus 50.degree. C. or higher is often cited by wire and cable manufacturers as desirable, particularly for installations in, for example, Canada.
A typical power cable is constructed of metal conductors insulated with a polymeric material. These elements are generally twisted to form a core and are protected by another polymeric sheath or jacket material. In certain cases, added protection is afforded by inserting a wrap between the core and the sheath.
Flame retardant compositions comprising polyethylene and magnesium hydroxide are useful in wire and cable applications, the polyethylene Providing flexibility and the magnesium hydroxide, flame retardance. Unfortunately, these compositions do not come close to meeting the most desirable low temperature performance as far as brittleness is concerned. It is difficult, for example, to achieve a low temperature brittleness of 0.degree. C. with a linear low density polyethylene flame retardant composition, let alone the desirable minus 50.degree. C.